The subject matter disclosed herein generally relates to gearboxes and, more particularly, to active peening of gears in an assembled gearbox.
Gears are used in various industrial and technological applications to permit power transmission from one rotating or translating element to another. Each gear generally includes an array of gear teeth that mesh with the gear teeth of another gear so that the rotation or translation of the first gear can be transmitted to the second. The forces on the gear teeth over time may cause failure of the gear, i.e., end of life of the gear. Conventional gearing or gears may be heat treated then final ground during manufacture to increase the strength and life of the gears and gear teeth. Enhancements to improve gear life beyond heat treatment and final grinding may include peening and superfinishing of the gear at the end of the manufacturing process. Such processes may increase compressive residual stresses and strength of the material forming the gear, the gear itself, and the gear teeth that may be subject to the highest impacts and forces during operation.
For example, peening may increase the compressive residual stress on gear tooth flanks and roots beyond the residual stresses induced during the heat treatment and final grinding processes of manufacture. These increased compressive residual stresses may result in higher load carrying capability and gear life as compared to non-peened gears.
However, as the gear is in service in a rotorcraft gearbox, i.e., in use, the compressive residual stresses imparted through the peening process may relax on the surface and may be redistributed through the gear tooth. With less compressive residual stress on the surface, load carrying capability may be reduced along with gear life.